Cross Connection Removal Project

Portions of the City of Modesto’s storm runoff are diverted into the sanitary sewer system through what are known as cross connections. In most cases, a cross pipe from a surface inlet or from a rock well directly connects to a sewer manhole. During heavy storm events these cross connections overburden the sewer system, Increase the cost for the wastewater treatment plant to treat the storm water, and occasionally lead to sanitary sewer overflows (SSO’s). The 2007 City of Modesto Waste Water Master Plan (WWMP) proposed to remove the cross connections due to this increased burden and cost.

We start with an existing park such as Garrison park (Pictured)

The park is excavated to completely submerge the storm chambers

The storm chambers are installed and crushed rock is used to fill the voids

Pre-Treatment Devices are Installed to remove contaminents from the storm water

The storm chambers are covered with dirt and new sprinklers are installed

Grass is then placed to cover the excavated area

The baseball field was renovated and a basketball court was added

The final result is a pleasantly soft, green play area and reduced storm water run off

There are 54 known cross connections throughout the city. The first phase of cross connection removal was completed in November 2014 and was referred to as Phase 1 Garrison Park (pictured above). The project removed 3 cross connections and twenty failed rock wells in the Carver/Orangeburg area. Several hundred feet of storm drain piping were installed to convey storm water from an approximate 24-acre tributary area to nearby Garrison Park where the storm water is pre-treated and then stored in underground percolation chambers. Additional benefits of the project are the reduction of local street flooding, improved water quality, and ground water recharge.